In a copending application of Cottam, Day and Griffith, three of the inventors here, Ser. No. 470,719, filed May 17, 1974, now U.S. Pat. No. 3,929,597 there is disclosed and claimed a lead and silver process in which the feed material such as ores and concentrates containing lead and silver sulfides are subjected to a more complex recovery process in which during the treatment the unroasted feed material or concentrate is subjected to successive treatments that include a first ferric leach, a second ferric leach, a first brine leach, a second brine leach and sodium sulfide leach leading to metallic lead and metallic silver. In the present process wherein the feed concentrate is first subjected to a neutral roasting which is at an elevated temperature and non-oxidizing atmosphere, certain chemical changes in the feed concentrate which are not understood as to their chemical nature take place so that the lead and silver ingredients are much more easily separated with the result that the process is greatly simplified in that the sodium sulfide leach, the second ferric leach and the second brine leach can be eliminated. Also, the percentage of silver and lead that are recovered are extraordinarily high. Thus in some embodiments the percentage of available silver in the feed concentrate is 97% recovered and the amount of lead is 99% recovered.
Thus this invention relates to the production of lead and silver metal from their sulfide materials such as ores and concentrates in a simplified process including as an essential step the roasting of these sulfide materials in a non-oxidizing atmosphere which can be reducing if desired at an elevated temperature followed by a ferric leach and then a brine leach of the resulting solids after which the filtrate which contains dissolved lead salt and dissolved silver salt is further treated to separate the lead and silver salts from the filtrate and from each other and the resulting solid is discarded as a final solid residue.
Other features and advantages of the invention will be apparent from the following description of one embodiment.